<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://unpkg.com/vue@next"></script>
</head>

<body>
    <div id="app"></div>
</body>
<script>
    let demo = {
        props: ['modelValue'],
        emits: ['update:modelValue'],
        template: `<div>
                    {{modelValue}}
                    <input 
                        :value="modelValue"
                        @input="$emit('update:modelValue',$event.target.value)"
                    />
                </div>`,
    }
    let vm = {
        data () {
            return {
                ipt: 'abc'
            }
        },
        components: { demo },
        template: `<demo v-model="ipt" />`,
    }
    let myVue = Vue.createApp(vm).mount('#app')
</script>

</html>